To make an alert that will tell you when a computer isn't up to date, go to Settings and then Monitors & Alerts and under "Add new Monitor" make the Type "Antivirus" and the condition should change automatically but if not, choose "is not up to date", select the group of computers to monitor and choose the option to email and hit Save.

Unfortunately no it will not tell you when AV is not installed. Only if it's out of date or has more than one AV installed.